Harnessing Scientific and Technological Advances to Improve Equity in Kidney Allocation Policies

Eplet-Predicted Antigens: An Attempt to Introduce Eplets into Unacceptable Antigen Determination and Calculated Panel-Reactive Antibody Calculation Facilitating Kidney Allocation

(1) Calculated panel-reactive antibody (CPRA) is a measure of sensitization based on unacceptable antigens (UAs). Determination of UAs based on single-antigen bead assays at allele or antigen levels may be inappropriate. We aimed to introduce eplets for better assessment of sensitization; (2) 900 recipients and 1427 donors were enrolled for candidate or donor pools, respectively. Eplets were from the HLA Epitope Registry. UAs were determined by anti-HLA antibodies identified using LIFECODES Single Antigen (LSA) kits. CPRA values were calculated using a simplified method of donor filtering; (3) HLA antigens containing all eplets of an HLA antigen in LSA kits (LSA antigen) were defined as eplet-predicted (EP) antigens, the reactivity of which could be predicted by that LSA antigen. High reactivity concordance was found between LSA and EP antigens. More HLA antigens were covered by EP antigens in the population than LSA antigens. CPRA values at the EP level were higher than at the allele level and lower than at the antigen level. The EP antigens facilitated UA determination for non-LSA antigens and avoided acute rejection; (4) UA determination using EP antigens can lead to more accurate assessment of sensitization, enabling a high probability of compatible organs and a low risk of adverse outcomes.

Significance of HLA-DQ in kidney transplantation: time to reevaluate human leukocyte antigen matching priorities to improve transplant outcomes? An expert review and recommendations

The weight of human leukocyte antigen (HLA) matching in kidney allocation algorithms, especially in the United States, has been devalued in a stepwise manner, supported by the introduction of modern immunosuppression. The intent was further to reduce the observed ethnic/racial disparity, as data emerged associating HLA matching with decreased access to transplantation for African American patients. In recent years, it has been increasingly recognized that a leading cause of graft loss is chronic antibody-mediated rejection, attributed to the development of de novo antibodies against mismatched donor HLA expressed on the graft. These antibodies are most frequently against donor HLA-DQ molecules. Beyond their impact on graft survival, generation of de novo donor-specific HLA antibodies also leads to increased sensitization, as measured by panel-reactive antibody metrics. Consequently, access to transplantation for patients returning to the waitlist in need of a second transplant is compromised. Herein, we address the implications of reduced HLA matching policies in kidney allocation. We highlight the observed diminished outcome data, the significant financial burden, the long-term health consequences, and, more important, the unintended consequences. We further provide recommendations to examine the impact of donor-recipient HLA class II and specifically HLA-DQα₁β₁ mismatching, focusing on collection of appropriate data, application of creative simulation approaches, and reconsideration of best practices to reduce inequalities while optimizing patient outcomes.

Removing administrative boundaries using a gravity model for a national liver allocation system

Geographic disparities emerged as an increasing issue in organ allocation policies. Because of the sequential and discrete geographical models used for allocation scores, artificial regional boundaries may impede the access of candidates with the greatest medical urgency to vital organs. This article describes a continuous geographical allocation model that provides accurate organ access by introducing a multiplicative interaction between the patient's condition and the distance to the graft by using a gravity model. Patients with the most urgent need will thus have access to organs from farther away, while those in less urgent need may only have access to organs geographically closer. Compared to the previous French liver allocation scheme, the gravity model precluded transplantations for candidates with a Model for End-Stage Liver Disease (MELD) ≤ 14 for decompensated cirrhosis from 10.3% to 0.6%. Death and delisting while on the waiting list at 1 year also decreased from 30.1% to 22.4% for MELD ≥ 35. Waiting list (cumulative hazard ratio (CHR)  0.84 after adjustment) and posttransplant survival improved significantly (hazard ratio = 0.83 after adjustment). This new liver allocation system provides more equitable access to liver transplants and an efficient and safe alternative to administrative boundaries for geographical models in organ allocation.

Clinical importance of extended second field high-resolution HLA genotyping for kidney transplantation

The need for extended second field high-resolution (2F-HR) HLA genotyping in kidney transplantation is debated. In a cohort of 1000 kidney transplants, we evaluated the impact of different HLA genotyping levels on the assignment of donor-specific anti-HLA antibodies (DSA) and investigated whether inference of 2F-HR genotypes from low-resolution (LR) genotypes could be used to correctly assign DSA. Based on LR genotypes, 224 pretransplant DSAs were present in 140 patients and absent in 860 patients (DSA_neg group). With extended 2F-HR HLA genotyping, we confirmed 173 DSA (77.2%) in 108 (77.1%) patients (2F-HR_pos LR_pos DSA group) and excluded DSA in 32 patients (22.9%) (2F-HR_neg LR_pos DSA group). Kaplan-Meier curves showed that 10-year graft survival rates were similar between the DSA_neg and 2F-HR_neg LR_pos DSA groups (82.4% vs 93.8%; P = .27) and confirmed that DSA determined using LR typing but not confirmed using 2F-HR typing were indeed misclassified. By inferring 2F-HR genotypes using HaploStats, DSA still could not be correctly assigned in 23.3% of cases. We conclude that extended 2F-HR typing of the donor-recipient pairs is relevant for the correct assessment of DSA. Although inference of 2F-HR genotypes may improve the assessment of DSA in some cases, significant misclassification occurs, and warrants caution in using inferred HLA results for clinical and research purposes.